The present invention relates to an ink jet recording method which provides an image having a good quality using a multiple channel head recording device. The invention further relates to an lithographic printing method and apparatus which carries out digital-plate making on a press using the ink jet recording method, a plate making method and apparatus which carries out the digital-plate making, and an ink jet printing method and apparatus.
As a method for applying an ink jet recording method to a printing system, a method for additionally printing variable numbers, marks, etc., on the same sheets of paper with the ink jet system by additionally attaching an ink jet printing apparatus to a rotary press has been disclosed in, for example, Japanese Patent Unexamined Publication No. Hei-10-286939.
It is preferable that high quality image information such as photographic images can be printed. However, since a great deal of liquid drops including much solvent is ejected in an ink technology for jetting aqueous or organic solvent-based ink, which includes conventional dyes or pigments as coloring agents, under pressure, there is a problem in that ink blurs out onto a printed image unless expensive specialty sheets of paper are used.
Therefore, where printing images on normal sheets of paper or plastic sheets of a non-absorbing type, no high quality printed image can be obtained.
In addition, as one of the ink jet technologies, there is a method in which ink that is solid in a normal temperature is heated and melted, and an image is formed by jetting the liquefied ink. The blurring of printed images may be reduced by using the ink. However, since the viscosity of the ink is high when ejecting the same, it is difficult to jet minute drops of ink, and individual dot images thus obtained become large in area and thick, wherein it is difficult to form highly fine images.
In the ink jet recording method using the conventional multiple channel head, when image recording is effected with an image resolution of 600 dpi, the various electrodes of the head each have a size of about 126 xcexcm, which corresponds to about 200 dpi, under restrictions in working. Accordingly, explaining 4-channel head as an example as shown in FIG. 11, the various ejection electrodes 56-(1) to 56-(4) each move by two steps each being about 42 xcexcm, which corresponds to 600 dpi, and skipped by 10 steps to continue image recording.
In this case, however, a so-called cross talk phenomenon occurs, causing ink particles to be exhausted in the head and hence reducing the diameter of dots thus formed or disabling ejection.
Further, adjacent ink droplets which have been ejected are off the course which they should follow during flying due to electrostatic repulsion, occasionally deteriorating the precision in the hitting position.
On the other hand, in the field of lithographic printing, ink receptive areas and ink repellent areas are formed on a surface of a printing plate in accordance with an original image. Printing ink adheres to the ink receptive areas to effect printing. Ordinarily, hydrophilic areas and oleophilic (ink receptive) areas are formed imagewise on the surface of a printing plate, and the hydrophilic areas are converted to oil-based ink repellent areas by applying dampening water thereto.
Conventional image recording (plate-making) on a printing original plate is carried out by exposing a silver salt photographic film with the desired image in an analog or digital manner, exposing a photopolymer material (printing original plate) containing a diazo resin or a photopolymerizable polymer to light through the silver halide photographic film, and then dissolving out the non-image areas mostly with an alkaline solution.
With recent improvements in digital recording technology and the demand for more efficient printing processes, various methods where digital image information is directly recorded on a printing original plate have been proposed in the field of lithographic printing method. These methods include technologies referred to a CTP (computer-to-plate) and a DDPP (digital direct printing plate) method. As the plate making method, there is provided a system where the image is recorded in a photon mode or heating mode using a laser beam. Some of these methods have been put to practical use.
However, after the image is recorded on a plate using either the photon mode or the heating mode, the non-image areas are dissolved out by treating the plate with an alkaline developer, resulting in the discharge of an alkaline waste liquid, which is environmentally undesirable.
As a means of carrying out the printing process at an enhanced efficiency there is proposed a system in which image recording is carried out on the press. The foregoing method involving the use of laser may be employed. However, this method requires an expensive and large-sized apparatus. Thus, a system utilizing an ink jet method which employs an inexpensive and compact image recording apparatus has been attempted.
Japanese Patent Unexamined Publication No. Hei. 4-97848 discloses a method which comprises forming an oleophilic or hydrophilic image on a plate drum, which is hydrophilic or oleophilic on the surface thereof instead of the conventional plate cylinder, by an ink jet process, and then removing the image after printing to clean the plate drum. However, this method is disadvantageous in that the desired removability of printed image (i.e., cleanability) and press life cannot be accomplished at the same time. In order to form a printed image having a prolonged press life on the plate cylinder, it is necessary that an ink containing a resin in a relatively high concentration be used. Thus, in the ink jet recording means for forming a printed image, the resin can be easily solidified due to the evaporation of solvent at the nozzle, deteriorating the stability in the ejection of ink. As a result, a good image can hardly be obtained.
Further, Japanese Patent Unexamined Publication No. sho. 64-27953 discloses a plate-making method which comprises recording an image of an oleophilic wax ink on a hydrophilic plate material by an ink jet process. In this method, since the image is formed of a wax, the resulting image area has a reduced mechanical strength and the adhesion of the image area to the hydrophilic surface of the plate material is insufficient, reducing the press life.
It is an object of the present invention to provide an ink jet recording method using a multiple channel head which can give an image having an extremely high and stable quality. Further, it is an object of the present invention to provide a lithographic printing method and apparatus for use with a digital recording system requiring no development process. It is another object of the present invention to provide a lithographic printing method and apparatus capable of providing a large number of prints having sharp images of high quality by an inexpensive apparatus and a simplified method. Further, it is still another object of the invention to provide a plate making method and a plate making apparatus for use with a digital recording system requiring no development process. In addition, it is still another object of the invention to further provide an ink jet printing method capable of providing a print having sharp images of high quality by an inexpensive apparatus and a simplified method.
(1) An on-press recording type lithographic printing method comprising mounting a plate material on a plate cylinder of a press, ejecting an oil-based ink onto the plate material from a recording head having a plurality of ejection channels utilizing an electrostatic field according to signals of image data to directly form an image on the surface of the plate material and prepare a printing plate, and then effecting the lithographic printing using the printing plate as it is,
wherein the distance of the ejection channels is 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded image}.
(2) The on-press recording type lithographic printing method according to (1), wherein said oil-based ink is a dispersion comprising resin particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(3) An on-press recording type lithographic printing apparatus comprising an image forming means for directly forming an image onto a plate material mounted on a plate cylinder of a press by using an ink jet recording device which ejects an oil-based ink from a recording head having a plurality of ejection channels according to signals of image data utilizing an electrostatic field, a lithographic printing means for effecting a lithographic printing using a printing plate formed by said image forming means,
wherein image forming means includes the recording head having the distance of the ejection channels being 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded image}.
(4) The on-press recording type lithographic printing apparatus according to (3), wherein said oil-based ink is a dispersion comprising resin particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(5) The on-press recording type lithographic printing apparatus according to (3) or (4), wherein said image forming means includes a device for fixing the ink.
(6) The on-press recording type lithographic printing apparatus according to any one of (3) to (5), wherein said image forming means includes plate material surface dust removing means for removing dust present on the surface of the plate material before and/or during the recording of an image on the plate material.
(7) The on-press recording type lithographic printing apparatus according to any one of (3) to (6), wherein said image forming means carries out main scanning by rotations of the plate cylinder mounted on the plate material.
(8) The on-press recording type lithographic printing apparatus according to (7), wherein said ink jet recording-device carries out subscanning by the recording head approaching and seperating in an axial direction of said plate cylinder when recoding an image on said plate material.
(9) The on-press recording type lithographic printing apparatus according to any one of (3) to (8), wherein said ink jet recording device includes ink supplying means for supplying the oil-based ink into the recording head.
(10) The on-press recording type lithographic printing apparatus according to (9), further comprising ink recovering means for recovering the oil-based ink from the recording head,
wherein ink circulation is carried out by the ink supplying means and the ink recovering means.
(11) The on-press recording type lithographic printing apparatus according to any of (3) to (10), further comprising ink stirring means in an ink tank housing the oil-based ink.
(12) The on-press recording type lithographic printing apparatus according to any of (3) to (11), further comprising ink temperature controlling means for controlling the temperature of the ink in the ink tank housing the oil-based ink.
(13) The on-press recording type lithographic printing apparatus according to any one of (3) to (12), further comprising an ink concentration controlling means for controlling the concentration of the ink.
(14) The on-press recording type lithographic printing apparatus according to any of (3) to (13), wherein said ink jet recording device includes recording head approaching and separating means for moving the recording head away from the plate cylinder except when recording the image on the plate material.
(15) The on-press recording type lithographic printing apparatus according to any of (3) to (14), wherein said image forming means includes recording head cleaning means for cleaning the recording head at least after the termination of plate making.
(16) The on-press recording type lithographic printing apparatus according to any of (3) to (15), wherein said lithographic printing means includes paper dust removing means for removing paper dust during lithographic printing.
(17) A plate making method comprising directly forming an image on a plate material and preparing a printing plate by recording using an ink jet method which ejects an oil-based ink from a recording head having a plurality of ejection channels according to signals of image data utilizing an electrostatic field, a lithographic printing means for effecting a lithographic printing using a printing plate formed by said image forming means,
wherein the formation of the image onto the plate material is carried out by the recording head having the distance of the ejection channels being 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded imager}.
(18) The plate making method according to (17), wherein said oil-based ink is a dispersion comprising resin particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(19) A plate making apparatus comprising image forming means for directly forming an image on a plate material by an ink jet recording device which ejects an oil-based ink from a recording head having a plurality of ejection channels according to signals of image data utilizing an electrostatic field,
wherein the formation of the image onto the plate material is carried out by the recording head having the distance of the ejection channels being 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded image}.
(20) The plate making apparatus according to (19), wherein said oil-based ink is a dispersion comprising resin particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(21) The plate making apparatus according to (19) or (20), wherein said image forming means includes a device for fixing the ink.
(22) The plate making apparatus according to any one of Claims (19) to (21), wherein said image forming means includes plate material surface dust removing means for removing dust present on the surface of the plate material before and/or during the recording of an image on the plate material.
(23) The plate making apparatus according to any one of (19) to (22), wherein the image is recorded by causing a printing medium to move by rotating the drum having the plate material mounted thereon when recording an image on the plate material.
(24) The plate making apparatus according to (23), wherein the image is recorded by causing the recording head to move in an axial direction of said drum.
(25) The plate making apparatus according to any one of (19) to (22), wherein when recording the image on the plate material, subscanning is carried out by causing said plate material to move with the same pinched by at least a pair of capstan rollers.
(26) The plate making apparatus according to (25), wherein said recording head is moved in the direction orthogonal to a traveling direction of said plate material.
(27) The plate making apparatus according to any one of (19) to (26), wherein said ink jet recording device includes ink supplying means for supplying the oil-based ink into the recording head.
(28) The plate making apparatus according to (27), further comprising ink recovering means for recovering the oil-based ink from the recording head,
where the ink circulation is carried out.
(29) The plate making apparatus according to any one of (19) to (28), wherein the ink jet recording device includes ink stirring means for stirring the oil-based ink in the ink tank housing the oil-based ink.
(30) The plate making apparatus according to any one of (19) to (29), wherein the ink jet recording device includes ink temperature controlling means for controlling the temperature of the oil-based ink in the ink tank housing the oil-based ink.
(31) The plate making apparatus according to any one of (19) to (30), wherein the ink jet recording device includes ink concentration controlling means for controlling the concentration of the oil-based ink.
(32) The plate making apparatus according to any one of (19) to (31), further comprises cleaning means for cleaning the recording head.
(33) A printing method comprising directly forming an image onto a printing medium and producing a print by an ink jet method which ejects an oil-based ink from a recording head having a plurality of ejection channels according to signals of image data utilizing an electrostatic field,
wherein the formation of the image onto the printing medium is carried out by the recording head having the distance the image forming means includes the recording head having the distance of the ejection channels being 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded image}.
(34) The ink jet printing method according to (33), wherein said oil-based ink is a dispersion comprising colored particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(35) A printing apparatus comprising image forming means for directly forming an image onto a printing material by an ink jet recording device which ejects an oil-based ink from a recording head having a plurality of ejection channels according to signals of image data utilizing an electrostatic field,
wherein the formation of the image onto the printing medium is carried out by the recording head having the distance the image forming means includes the recording head having the distance of the ejection channels being 170 xcexcm or more {150 dpi (150 dots per inch) or less as calculated in terms of resolution of recorded image}.
(36) The printing apparatus according to (35), wherein said oil-based ink is a dispersion comprising colored particles which are solid and hydrophobic at least at ordinary temperature dispersed in a nonaqueous solvent having an inherent electrical resistance of 109 xcexa9-cm or more and a dielectric constant of 3.5 or less.
(37) The printing apparatus according to (35) or (36), wherein the image forming means includes a device for fixing the ink.
(38) The printing apparatus according to any one of (35) to (37), further comprising dust removing means for removing dust present on the surface of the printing medium before and/or during the printing onto the printing medium.
(39) The printing apparatus according to any one of (35) to (38), wherein when recording onto the printing medium, the image is recorded via the printing medium by causing the printing medium to move by rotating an opposed drum, which is disposed at the position opposed to the recording head.
(40) The printing apparatus according to (39), wherein the image is recorded by causing said recording head to move in an axial direction of said opposed drum.
(41) The printing apparatus according to (35) to (38), wherein when recording onto the printing medium, the image is recorded by causing said printing medium to move with the same pinched by at least a pair of capstan rollers.
(42) The printing apparatus according to (41), wherein the image is recorded by causing said recording head to move in the direction orthogonal to a traveling direction of said printing medium.
(43) The printing apparatus according to any one of (35) to (42), wherein the ink jet recording device includes ink supplying means for supplying the oil-based ink into the recording head.
(44) The printing apparatus according to (43), further comprising ink recovering means for recovering the oil-based ink from the recording head,
wherein the ink circulation is carried out.
(45) The printing apparatus according to any one of (35) to (44), wherein the ink jet recording device includes ink stirring means for stirring the oil-based ink in the ink tank housing the oil-based ink.
(46) The printing apparatus according to any one of (35) to (45), wherein the ink jet recording device includes ink temperature controlling means for controlling the temperature of the oil-based ink in the ink tank housing the oil-based ink.
(47) The printing apparatus according to any one of (35) to (46), wherein the ink jet recording device includes ink concentration controlling means for controlling the concentration of the oil-based ink.
(48) The printing apparatus according to any one of (35) to (47), further comprising cleaning means for cleaning the recording head.